Tire pressure sensors for monitoring tire pressure have been under development for some time. Since such sensors are typically disposed on the tire being monitored, various sensor attachment/packaging approaches have been considered. For example, in U.S. Pat. No. 4,763,517, a sensor is mounted in the cap of a tire valve stem. More commonly, sensors have been attached to and/or integrated with modified valve stems of various kinds.
For example, in US 2004/0046649, a sensor is attached to a metal bore of a valve stem, which can serve as an antenna for the sensor. In U.S. Pat. No. 4,310,014, a modified tire valve stem is employed, having a pressure sensor integrated with the valve stem. In U.S. Pat. No. 5,844,131, a sensor is connected to a metal tire valve stem with a hollow screw that engages into the valve bore.
One commonly employed type of tire valve stem is the so-called “snap-in” tire valve stem, which has been in use for many years. For example, a snap-in tire valve stem is described in U.S. Pat. No. 2,968,333, issued in 1961. A snap-in tire valve stem includes a metal tube surrounded by and bonded to a flexible valve stem body, where the flexible valve stem body is configured to snap in to a valve opening of a wheel rim, and the metal tube is configured to accommodate a valve. Part of the bore of a standard snap-in tire valve stem is flexible, in order to provide the above-described snap-in functionality.
Several approaches have been demonstrated for attaching a sensor to a snap-in tire valve stem. For example, in U.S. Pat. No. 6,005,480, the sensor is engaged with the metal tube of the tire valve stem, by threads or a press fit. In U.S. Pat. No. 6,722,409, a snap-in tire valve stem is fabricated having a second metal insert within it, to which a sensor can be attached.
The snap-in concept has also been applied in a somewhat different manner in U.S. Pat. No. 7,086,412 and US 2005/0087007. In this work, a snap-in grommet is employed having an outer flexible body surrounding a metal sleeve. The valve stem and sensor are both attached to the metal sleeve of the grommet.
However, these prior art approaches tend to suffer from the disadvantage that substantial modification of an otherwise standard valve stem is required to permit sensor attachment. For example, the snap-in valve stem of U.S. Pat. No. 6,005,480 must have a metal tube that is threaded or capable of making a press fit connection with a sensor package, thereby making it a non-standard part. Similarly, the snap-in valve stem of U.S. Pat. No. 6,722,409 is made with a second metal insert, again making it a non-standard part.
Accordingly, it would be an advance in the art to provide attachment of a sensor to a standard snap-in tire valve stem.